For example, a company which produces a color printed matter such as a printing company regularly measures the color of the printed matter and adjusts colors of a printing apparatus having printed that printed matter to maintain the quality of the printed matter. In such a color adjustment of the printing apparatus, raw image data called a color chart is, for example, printed by the printing apparatus and the color of each patch in this printed color chart is measured by a colorimetry device. A color shift amount between an actually measured value of the color of each patch and a target value of the color of each patch is evaluated and the colors of the printing apparatus are adjusted according to this evaluation result.
The color chart is composed of a plurality of color samples called the patches, and a plurality of patches are in mutually different colors (hue, intensity, saturation) in many cases, and are arranged in a predetermined mode. Such color charts come in various types. For example, there are color charts configured by arranging a plurality of square patches having various colors in vertical and horizontal directions in a two-dimensional array. Color charts of such a mode have various patterns depending on contents to be evaluated such as by arranging the respective patches to have a random color array and arranging the respective patches to reduce a change in shading between the patches adjacent to each other as in gradation. Such color charts are not only produced by a user using a color chart production tool provided by a manufacturer of the colorimetry device, but also provided from a public institution. As just described, color charts have, indeed, various patterns due to differences in the shape, arrangement, color scheme and the like of patches.
On the other hand, the number of colors used in the color adjustment of a printing apparatus is increasing year by year. According to this, the number of patches arranged in a color chart is also increasing and, in addition, the size (area) of each patch is small.
Due to such circumstances, it has become practically impossible to measure color by manually precisely aligning a measuring part of the colorimetry device with each patch. Thus, a system is desired which automatically measures the position of each patch, automatically aligns the measuring part of the colorimetry device with the measured position of each patch and automatically measures the color of each patch. As an example of such a system, a method for capturing a two-dimensional color image of a color chart desired to be measured, calculating the positions of patches by an image processing technique using a computer and moving a color measuring head to the determined patch positions to measure colors of the color chart is proposed in patent literature 1 by Gretag-Macbeth.
As described above, color charts come in various types. Color charts of one type include not only a chart region where a plurality of patches are present, but also a normal image region where a normal image obtained by imaging a landscape, animal(s)/plant(s), people/people, goods, character(s) (symbol(s)) or the like is present. Whether or not a target region is a chart region is not discriminated in the patch position automatic measuring method for automatically measuring the positions of the patches disclosed in the above patent literature 1. Thus, if a color chart including such a normal image region is measured, the positions of the patches is measured with the normal image region also as a measurement object. Thus, in the patch position automatic measuring method disclosed in the above patent literature 1, the positions of the patches may be erroneously detected. Further, a user may desire the measurement of the colors of some of the detected patches.